EP1468208B1

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Info

Publication number: EP1468208B1
Application number: EP03707311A
Authority: EP
Inventors: Michael C. Doyle; Barry Plato
Original assignee: Black and Decker Inc
Current assignee: Black and Decker Inc
Priority date: 2002-01-25
Filing date: 2003-01-07
Publication date: 2011-06-22
Anticipated expiration: 2023-01-07
Also published as: EP1468208A1; ATE514016T1; MXPA04007158A; CN1643270A; TW200302145A; DE10362193B4; TWI263551B; EP1468208A4; BR0307083A

Abstract

A hand-held power tool having a multi-speed transmission and a clutch. The multi-speed transmission and the clutch are coupled to one another via a set of interconnecting tabs that are slidingly engaged to one another and secured with pins to inhibit the withdrawal of the tabs from one another. The clutch may include a clutch member, a unitarily formed clutch plate and a plurality of engagement members. The clutch plate includes an annular plate member and a plurality of leg members that extend generally perpendicularly from the annular plate member and which bias the engagement members into engagement with the clutch member. The clutch member may be coupled to an element of the multi-speed transmission, such as to the ring gear of a planetary gear set, so as to reduce the overall size of the power tool.

Description

FIELD OF THE INVENTION

The present invention generally relates to power tools such as rotatable drills, power screwdrivers, and rotatable cutting devices. More specifically, the present invention relates to improvements in power tools and more particularly to the construction of a clutch mechanism and its coupling to a transmission.

BACKGROUND OF THE INVENTION

Modernly, manufacturers of power tools desire to reduce the cost of producing power tools by providing designs that provide the product with a high level of robustness while reducing complexity at the assembly level and minimizing components that do not add value to the product. Manufacturers are further challenged by the demand of modern consumers for tools that are relatively smaller in size, lighter in weight and more powerful.

Accordingly, it is highly desirable to eliminate threaded fasteners from the power tool, such as those that are typically employed to couple the transmission assembly to the clutch mechanism. The use of threaded fasteners in these situations necessitates the incorporation of bosses to the transmission assembly and the clutch mechanism that tend to enlarge the size of the tool and which add a degree of weight to the power tool. The fastening process itself tends to be relatively slow and errors in the process, such as over tightening, which can lead to the stripping of threads or cracking of the components, or under tightening, which can create an interference that prevents the components from operating properly, are possible. The use of torque controlled fastening equipment is known to alleviate such processing errors, but this equipment can be relatively expensive to purchase and operate.

It is also desirable to better integrate the clutch mechanism with the transmission assembly. Many of the known power tool designs employ a modular design that is based on a power tool having no torque controlled clutch. In cases where precise torque control was needed, a clutch module could be coupled to the output end of the base tool. While configuration in this manner effectively accommodated consumer demands for both the base and torque controlled models in an economical manner, the modular configuration tended to add considerable length and weight to the power tool.
A hand held power tool according to the preamble of claim 1 is described in DE20010286.

SUMMARY OF THE INVENTION

According to the present invention, there is provided a hand held power tool comprising the features of claim 1.
In one preferred form, the present invention provides a coupling mechanism for coupling the components of a power tool, such as a transmission assembly and a clutch mechanism. The coupling mechanism includes a first structure, such as a gear case, having at least one fastening tab that defines a coupling recess. The coupling mechanism also includes a second structure, such as a clutch sleeve, having an aperture for receiving a part of the first structure, and at least one outboard tab for receiving the fastening tab or tabs. The outboard tab(s) include a pin aperture that is aligned to the coupling recess when the first and second structures are fitted together. A pin is placed into each pin aperture and an associated coupling recess and operates to lock the fastening tab within the outboard tab to thereby inhibit relative movement between the first and second structures.
In another preferred form, the present invention provides a power tool having an improved clutch mechanism for limiting the torsional output of a transmission assembly. The clutch mechanism includes a clutch member that is fixedly coupled to a portion of the transmission assembly, such as the ring gear of a planetary-type reduction gear set. The clutch member includes a contoured clutch face against which a rotation-inhibiting element is biased. The torsional output of the transmission assembly is limited by the force that is exerted by the rotation-inhibiting element onto the clutch face. When the torque that is exerted on the portion of the transmission assembly exceeds a predetermined magnitude, the clutch member, along with the portion of the transmission assembly, rotates relative to the rotation inhibiting element to thereby limit the torsional output of the power tool.
In yet another preferred form, the present invention provides an improved clutch mechanism. The clutch mechanism includes a unitarily formed clutch plate having an annular plate member and a plurality of legs that extend outwardly from the annular plate member toward a clutch member. The opposite end of the legs may be contoured to receive force-transmitting elements, such as bearing balls, which are employed to transmit a biasing force to the clutch member to bias the clutch member in a stationary condition. Alternatively, the opposite ends of the legs may be contoured to act as force transmitting elements.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein:
Figure 1 is a side view of a power tool constructed in accordance with the teaching of the present invention;
Figure 2 is an exploded perspective view of a portion of the power tool ofFigure 1;
Figure 3 is an enlarged view of a portion ofFigure 2 illustrating the transmission assembly and the clutch mechanism in greater detail;
Figure 4 is an exploded perspective view of a portion of the power tool ofFigure 1 illustrating the construction of the gear case and the clutch sleeve;
Figure 5 is a sectional view of a portion of the power tool ofFigure 1 taken along the longitudinal axis of the power tool and illustrating the construction of the transmission assembly;
Figure 6 is a sectional view of a portion of the transmission assembly illustrating the second planetary gear set in the active position;
Figure 7 is a perspective view of a portion of the transmission assembly illustrating the contour of the top and rear surfaces of the second reduction carrier;
Figure 8 is a perspective view of a portion of the transmission assembly illustrating the third ring gear in greater detail;
Figure 9 is a sectional view taken along the line 9-9 ofFigure 3;
Figure 10 is a partial bottom view of a portion of the transmission assembly illustrating the speed selector mechanism in greater detail;
Figure 11 is a sectional view of a portion of the power tool ofFigure 1 taken through the gear case and clutch sleeve and illustrating the method by which the transmission assembly and the clutch mechanism are coupled;
Figure 12 is a side view of a the clutch plate;
Figure 13 is an exploded side view in partial section illustrating the clutch plate and the balls;
Figure 14 is a sectional view similar to that ofFigure 13 but illustrating an alternate embodiment of the clutch plate; and
Figure 15 is a sectional view of a portion of the power tool ofFigure 1 taken along the longitudinal axis and illustrating the clutch mechanism in greater detail.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference toFigures 1 and2 of the drawings, a power tool constructed in accordance with the teachings of the present invention is generally indicated byreference numeral 10. As those skilled in the art will appreciate, the preferred embodiment of the present invention may be either a cord or cordless (battery operated) device, such as a portable screwdriver or drill. In the particular embodiment illustrated, thepower tool 10 is a cordless drill having ahousing 12, amotor assembly 14, amulti-speed transmission assembly 16, aclutch mechanism 18, anoutput spindle assembly 20, achuck 22, atrigger assembly 24 and abattery pack 26. Those skilled in the art will understand that several of the components of thepower tool 10, such as thechuck 22, thetrigger assembly 24 and thebattery pack 26, are conventional in nature and therefore need not be discussed in significant detail in the present application. Reference may be made to a variety of publications for a more complete understanding of the conventional features of thepower tool 10. One example of such publications isU.S. Patent No. 5,897,454 issued April 27, 1999.
Thehousing 12 includes a pair ofmating handle shells 34 that cooperate to define ahandle portion 36 and a drive train orbody portion 38. Thetrigger assembly 24 and thebattery pack 26 are mechanically coupled to thehandle portion 36 and electrically coupled to themotor assembly 14 in a conventional manner that is not specifically shown but which is readily the capabilities of one having an ordinary level of skill in the art. Thebody portion 38 includes amotor cavity 40 and atransmission cavity 42. Themotor assembly 14 is housed in themotor cavity 40 and includes arotatable output shaft 44, which extends into thetransmission cavity 42. Amotor pinion 46 having a plurality ofgear teeth 48 is coupled for rotation with theoutput shaft 44. The trigger assembly andbattery pack 26 cooperate to selectively provide electric power to themotor assembly 14 in a manner that is generally well known in the art so as to permit the user of thepower tool 10 to control the speed and direction with which theoutput shaft 44 rotates.
Thetransmission assembly 16 is housed in thetransmission cavity 42 and includes aspeed selector mechanism 60. Thetransmission assembly 16 receives a rotary input from themotor pinion 46 and converts that input to a relatively lower speed, higher torque output that is transmitted to theshaft 62 of theoutput spindle assembly 20. Thetransmission assembly 16 includes a plurality of reduction elements that are selectively engaged by thespeed selector mechanism 60 to provide a plurality of speed ratios. Each of the speed ratios multiplies the speed and torque of the drive input in a predetermined manner, permitting the output speed and torque of thetransmission assembly 16 to be varied in a desired manner between a relatively low speed, high torque output and a relatively high speed, low torque output. Rotary power output from thetransmission assembly 16 is transmitted to the output spindle assembly, to which thechuck 22 is coupled for rotation, to permit torque to be transmitted to a tool bit (not shown). Theclutch mechanism 18 is coupled to the transmission assembly and is operable for limiting the magnitude of the torque associated with the output of thetransmission assembly 16 to a predetermined, selectable torque limit.

Transmission Assembly

With additional reference toFigure 3, thetransmission assembly 16 is illustrated to further include agear case 100 that houses a three-stage, two-speed gear train 102. With additional reference toFigure 4, thegear case 100 is shaped in a generally hollow cylindrical manner and includes afastening tab 104 and aclip aperture 106 on each of its lateral sides, a pair ofguide rails 108 and aguide tab 110 that is located on its top surface, and acentral cavity 112 that extends longitudinally through thegear case 100. Eachfastening tab 104 terminates at its outward face at acoupling recess 114 that extends in a direction that is generally transverse to thecentral cavity 112. Thecoupling recess 114 is preferably arcuately shaped, and in the particular embodiment illustrated, is illustrated to be generally U-shaped. Eachclip aperture 106 extends through thewall 116 of thegear case 100 along thelongitudinal axis 118 of thecentral cavity 112 and intersects thecentral cavity 112. The guide rails 108 positioned rearwardly of theguide tab 110 and are spaced laterally apart from one another. The guide rails 108 and theguide tab 110 will be discussed in further detail, below.
Thegear train 102 is illustrated to be a planetary type gear train, having a first planetary gear set 120, a second planetary gear set 122 and a third planetary gear set 124. In the example provided, each of the first, second and third gear sets 120, 122 and 124 are operable in an active mode, wherein the gear set performs a speed reduction and torque multiplication operation, while the second planetary gear set 122 is also operable in an inactive mode, wherein it provides a rotary output having a speed and torque that is about equal to that which is input to it.
The first planetary gear set 120 includesfirst ring gear 130, a first set of planet gears 132 and afirst reduction carrier 134. Thefirst ring gear 130 is an annular structure, having a plurality ofgear teeth 130a that are formed about its interior diameter and a plurality of gearcase engagement teeth 130b that are formed onto its outer perimeter. With additional reference toFigure 5, thefirst ring gear 130 is disposed within thecentral cavity 112 of thegear case 100 such that the gearcase engagement teeth 130b engagemating teeth 130c formed on the inner surface of thegear case 100 to inhibit relative rotation between thefirst ring gear 130 and thegear case 100. As the gearcase engagement teeth 130b terminate prior to therear face 130d of thefirst ring gear 130, forward movement of thefirst ring gear 130 is halted by interference between themating teeth 130c that are formed on the inner surface of thegear case 100 and the portion of thefirst ring gear 130 that is disposed rearwardly of the gearcase engagement teeth 130b.
Thefirst reduction carrier 134 includes abody 134a, which is formed in the shape of a flat cylinder and a plurality ofcylindrical pins 134b that extend from the rearward face of thebody 134a, and a plurality of 134c
A plurality ofgear teeth 134c are formed into the outer perimeter of thebody 134a and are sized to engage thegear teeth 152a of thesecond ring gear 152. With reference toFigure 7, the profile of thegear teeth 134c of thebody 134a is illustrated in greater detail. As shown, eachtooth 134c terminates at agradual radius 190 at the forward face of thebody 134a but terminates abruptly at the rearward face of thebody 134a. Aradius 192 is also formed on thevalleys 194 between thegear teeth 134c. The first set of planet gears 132 includes a plurality ofplanet gears 132a, each of which being generally cylindrical in shape and having a plurality ofgear teeth 132b formed onto its outer perimeter and a pin aperture (not specifically shown) formed through its center. Eachplanet gear 132a is rotatably supported on an associated one of thepins 132b of thefirst reduction carrier 134 and is positioned to be in meshing engagement with the gear teeth of thefirst ring gear 130. A firstannular thrust washer 140 is fitted to the end of thegear case 100 proximate themotor assembly 14 and prevents the planet gears 132 from moving rearwardly and disengaging thepins 134b of thefirst reduction carrier 134. A raisedportion 142 is formed onto the front and rear faces of eachplanet gear 132 to inhibit thegear teeth 132b of the planet gears 132 from rubbing on thefirst reduction carrier 134 and thefirst thrust washer 140. The teeth 46a of themotor pinion 46 are also meshingly engaged with theteeth 132b of the planet gears 132 and as such, themotor pinion 46 serves as the first sun gear for the first planetary gear set 120.
The second planetary gear set 122 is disposed within thecentral cavity 112 forward of the first planetary gear set 120 and includes asecond sun gear 150, asecond ring gear 152, a second reduction carrier 154 and a second set of planet gears 156. Thesecond sun gear 150 is fixed for rotation with thefirst reduction carrier 134 and includes a plurality ofgear teeth 150a that extend forwardly from the flat, cylindrical portion of thefirst reduction carrier 134.
Thesecond ring gear 152 is an annular structure having a plurality ofgear teeth 152a formed about its interior diameter, anannular clip groove 158 formed into its outer perimeter and a plurality of gearcase engagement teeth 160 that are formed onto its outer perimeter. Thegear teeth 152a may be heavily chamfered at therear face 152b of thesecond ring gear 152 but terminate abruptly its front face. More preferably, aheavy radius 170 is formed onto therear face 152b and the sides of each of thegear teeth 152a as illustrated inFigure 6, with theheavy radius 170 being employed rather than the heavy chamfer as theheavy radius 170 on thegear teeth 152a provides for better engagement between thesecond ring gear 152 and the second reduction carrier 154, as will be described in more detail, below. In the example illustrated, theclip groove 158 is a rectangular slot having a pair ofsidewalls 174. Theclip groove 158 will be discussed in further detail, below.
Thesecond ring gear 152 is movably disposed within thecentral cavity 112 of thegear case 100 between a first position as shown inFigure 6, wherein the gearcase engagement teeth 160 engagemating teeth 180 formed on the inner surface of thegear case 100 to inhibit relative rotation between thesecond ring gear 152 and thegear case 100, and a second position as shown inFigure 5, wherein the gearcase engagement teeth 160 are axially spaced apart from themating teeth 180 to thereby permit relative rotation between thesecond ring gear 152 and thegear case 100.
The second reduction carrier 154 includes a body 154a, which is formed in the shape of a flat cylinder, and plurality of pins 154b that extend from the rearward face of the body 154a.
Referring back toFigures 3 and5, the second set of planet gears 156 is shown to include a plurality ofplanet gears 156a, each of which being generally cylindrical in shape and having a plurality ofgear teeth 156b and a pin aperture (not specifically shown) in its center. Eachplanet gear 156a is supported for rotation on an associated one of the pins 154b of the second reduction carrier 154 and is positioned such that thegear teeth 156b are in meshing engagement withgear teeth 152a of thesecond ring gear 152.
The third planetary gear set 124 is disposed on the side of the second planetary gear set 122 opposite the first planetary gear set 120. Like the second planetary gear set 122, the third planetary gear set 124 includes athird sun gear 200, athird ring gear 202, athird reduction carrier 204 and a third set of planet gears 206. Thethird sun gear 200 is fixed for rotation with the body 154a of the second reduction carrier 154 and includes a plurality ofgear teeth 200a that extend forwardly from the body 154a. An annularsecond thrust washer 210 is disposed between thesecond ring gear 152 and thethird ring gear 202 and operates to limit the forward movement of thesecond ring gear 152 and the rearward movement of thethird ring gear 202 and the third set of planet gears 206. Thesecond thrust washer 210, which includes anaperture 212 through which thethird sun gear 200 extends, engages the inner surface of thegear case 100.
Thethird ring gear 202 is an annular structure having a plurality ofgear teeth 202a formed about its interior diameter and an outerradial flange 220 that forms its outer perimeter. Aclutch face 222 is formed into the forward surface of the outerradial flange 220. In the particular embodiment illustrated, theclutch face 222 is shown to have an arcuate cross-sectional profile and is further defined by a plurality ofpeaks 224 and valleys 226 that are arranged relative to one another to form a series of ramps that are defined by an angle of about 18°. Those skilled in the art will understand, however, that clutch faces of other configurations, such as those having a sinusoidal shape, may also be employed. Those skilled in the art will also understand that while theclutch face 222 is shown to be unitarily formed with thethird ring gear 202, multi-component configurations may also be employed. Such multi-component configurations include, for example, an annular clutch face ring (not shown) having a rearward facing first side for engaging thethird ring gear 202 and a forward facing second side that forms theclutch face 222. Configuration in this latter manner may be advantageous, for example, when it is necessary for theclutch face 222 to have properties or characteristics (e.g., lubricity, hardness, toughness, surface finish) that are different from the properties or characteristics of thethird ring gear 202.
Thethird reduction carrier 204 includes abody 204a, which is formed in the shape of a flat cylinder, and a plurality ofcylindrical pins 204b, which extend from the rearward face of thebody 204a, and acoupling portion 204c that extends from the forward face of thebody 204a. Rotary power transmitted to thethird reduction carrier 204 is transmitted through thecoupling portion 204c to acoupling member 230 that engages the shaft 62of theoutput spindle assembly 20. Those skilled in the art will understand that various other coupling devices and methods may be utilized to couple thethird reduction carrier 204 to theoutput spindle assembly 20, such as a direct coupling of theshaft 62 of theoutput spindle assembly 20 to thebody 204a of thethird reduction carrier 204.
The third set of planet gears 206 includes a plurality ofplanet gears 206a, each of which being generally cylindrical in shape and having a plurality ofgear teeth 206b formed onto its outer perimeter and a pin aperture (not specifically shown) formed through its center. Eachplanet gear 206a is rotatably supported on an associated one of thepins 204b of thethird reduction carrier 204 and is positioned to be in meshing engagement with thegear teeth 202a of thethird ring gear 202.
Thespeed selector mechanism 60 is illustrated to include aslider body 240 and aclip structure 242. Theslider body 240 is an elongated structure that is configured to be housed between thehandle shells 34 and selectively slid along the top of thegear case 100. Theslider body 240 includes anattachment groove 246, which permits theclip structure 242 to be attached to theslider body 240, and aselector tab 248, which is configured to receive an input from the user of thepower tool 10 to switch the second planetary gear set 122 between the active and inactive modes. With additional reference toFigures 9 and 10, aslot 250 is formed into the underside of theslider body 240 and is sized to engage theguide tab 110 that extends from the top surface of thegear case 100. The guide rails 108 are spaced laterally apart to receive theslider body 240. Theguide tab 110 and theguide rails 108 cooperate with the sides of theslot 250 and the sides of theattachment groove 246, respectively, to guide theslider body 240 as theslider body 240 is moved in an axial direction along the top surface of thegear case 100.
Returning toFigure 3, theclip structure 242 is a wire that is formed to include acircular body portion 256 and a pair ofend tabs 258 that extend inwardly from thebody portion 256. Thebody portion 256 is fixedly coupled to anattachment tab 260, which is illustrated to be a pair of trunnions that extend downwardly from theslider body 240. Thebody portion 256 is sized to fit over the outer circumference of thegear case 100 and preferably includes a rotation-inhibitingelement 262 to inhibit theclip structure 242 from rotating relative to theattachment tab 260. In the embodiment provided, the rotation-inhibitingelement 262 is illustrated to include a plurality of bends, such as M-, N-, S-, or Z-shaped bends, that are formed into the wire and which are molded into or abut the underside of theslider body 240. Each of theend tabs 258 extends through an associated one of theclip apertures 106 in the sides of thegear case 100 and engages theannular clip groove 158 that is formed into the perimeter of thesecond ring gear 152. The wire that forms theclip structure 242 is somewhat smaller in diameter than the width of theclip groove 158.
Alternatively, the rotation-inhibitingelement 262 may include a plurality of tabs that are formed from bends in thebody portion 256 of the wire, wherein each tab is defined by a circumferentially extending segment that is offset radially outwardly from the remainder of thebody portion 256. Each of the tabs is configured to be received in a corresponding aperture formed into theslider body 240 such that the front and rear faces of each tab engage the sides of the apertures in theslider body 240. The tabs, being confined within an associated aperture in theslider body 240, inhibit relative movement between theslider body 240 and thebody portion 256 of theclip structure 242.
Sliding movement of theslider body 240 relative to thegear case 100 is operable for transmitting a force through theend tabs 258 of theclip structure 242 and to thesecond ring gear 152 which may be used to move thesecond ring gear 152 between the first and second positions. When thesecond ring gear 152 is positioned in the first position as illustrated inFigure 6, theengagement teeth 160 of thesecond ring gear 152 are engaged to themating engagement teeth 180 of thegear case 100 and thegear teeth 152a of thesecond ring gear 152 are engaged to only thegear teeth 156b of the planet gears 156a of the second planet gear set 156, thereby permitting the second planetary gear set 122 to operate in the active mode. When thesecond ring gear 152 is positioned in the second position as illustrated inFigure 5, theengagement teeth 160 of thesecond ring gear 152 are not engaged to themating engagement teeth 180 of thegear case 100 and thegear teeth 152a of thesecond ring gear 152 are engaged to both thegear teeth 156b of the planet gears 156a of the second planet gear set 156 and thegear teeth 134c of thefirst reduction carrier 134, thereby permitting the second planetary gear set 122 to operate in the inactive mode.

Clutch mechanism

InFigure 3, theclutch mechanism 18 is illustrated to include aclutch sleeve 300, aclutch member 302, a plurality ofballs 304, aclutch plate 306, aspring 308, anadjustment collar 310, adetent mechanism 312 and aclutch cover 314. With additional reference toFigure 4, theclutch sleeve 300 is illustrated to include awall member 320, which defines a hollow cavity or bore 322 that extends along the longitudinal axis of theclutch sleeve 300, abase portion 324 and anose portion 326 that extends forwardly from thebase portion 324. The rearward end of thebore 322 is sized to receive a forward portion of thegear case 100, thethird ring gear 202 and thethird reduction carrier 204, while the forward portion of thebore 322 is sized somewhat smaller so as to receive thecoupling member 230 and theshaft 62 of theoutput spindle assembly 20. Thenose portion 326, which is somewhat smaller in diameter than thebase portion 324, is generally cylindrical, having ahelical thread form 330 that wraps around its perimeter.
Thebase portion 324 includes a pair ofoutboard tabs 334, which are formed on the lateral sides of thebase portion 324, a plurality ofleg apertures 336, which extend generally perpendicular to the longitudinal axis of thebore 322, and a detent aperture 338 for receiving thedetent mechanism 312. Eachoutboard tab 334 is configured to receive an associated one of thefastening tabs 104 and includes apin aperture 340. In the particular embodiment illustrated, eachoutboard tab 334 is defined by an outerlateral wall 342, alower wall 344, and anupper wall 346, through which thepin aperture 340 extends. With additional reference toFigure 11, acylindrical locking pin 350 is fitted through thepin aperture 340 in eachoutboard tab 334 and thecoupling recess 114 in the associatedfastening tab 104 and thereby fixedly but removably couples theclutch sleeve 300 to thegear case 100. The locking pins 350 are highly advantageous in that they eliminate the need for threaded fasteners, fastening tools and the use of bosses in thegear case 100 and theclutch sleeve 300 that are configured for receiving a conventional threaded fastener. Theleg apertures 336 are circumferentially spaced about thenose portion 326 and extend through thebase portion 324 and intersect the rearward portion of thebore 322. The detent aperture 338 extends through thebase portion 324 between theclutch cover 314 and thegear case 100 and is sized to receive a portion of thedetent mechanism 312.
InFigures 3,12 and 13, theclutch plate 306 is illustrated to be a unitarily formed structure that includes a washer-likeannular plate member 360 and a plurality ofleg members 362 that are coupled to and circumferentially spaced about theannular plate member 360. Theleg members 362 have a generally circular cross-section and extend generally perpendicularly from theplate member 360. The end of the eachleg member 362 opposite theplate member 360 terminates in aspherical recess 364 that is configured to receive one of theballs 304, which are illustrated to be hardened bearing balls. Theclutch plate 306 is disposed over thenose portion 326 of theclutch sleeve 300 and moved axially rearward to push theleg members 362 through theleg apertures 336 in thebase portion 324, as well as to bring each of theballs 304 into contact with theclutch face 222 and an associated one of thespherical recesses 364.
In an alternate embodiment illustrated inFigure 14, the clutch plate 306' is illustrated to be similar to theclutch plate 306, except that the ends of the leg members 362' opposite theannular plate member 360 terminate at aspherical protrusion 370, rather than a spherical recess. Configuration in this manner is advantageous in that it eliminates theballs 304 from theclutch mechanism 18.
Returning toFigure 3 and with additional reference toFigure 15, thespring 308 is illustrated to be a conventional compression spring having ground ends. Thespring 308 is disposed over thenose portion 326 of theclutch sleeve 300 between theplate member 360 of theclutch plate 306 and theadjustment collar 310. Theadjustment collar 310 is an annular structure that is illustrated to include an internalannular flange 380, a threadedportion 382 and anengagement portion 384. The internalannular flange 380 extends around the inner circumference of theadjustment collar 310 and sized somewhat smaller in diameter than thespring 308 but larger than thenose portion 326 of theclutch sleeve 300. The threadedportion 382 intersects the internalannular flange 380 and is sized to threadably engage thethread form 330 that is formed on the outer diameter of thenose portion 326. Theengagement portion 384 is configured to permit theadjustment collar 310 to be rotatably coupled to theclutch cover 314 and well as to move axially within theclutch cover 314. In the example provided, theengagement portion 384 includes a plurality ofengagement teeth 384a that are formed about the outer perimeter of theadjustment collar 310. Theengagement teeth 384a will be described in further detail, below.
Awire clip 400 is coupled to thenose portion 326 to inhibit the removal of theadjustment collar 310 from thethread form 330. Thewire clip 400 is formed in U-shape, having a base 402 that is disposed between a pair of spaced apartlegs 404. Each of thelegs 404 extends in a generally perpendicular direction away from thebase 402. With theclutch plate 306 andspring 308 fitted over thenose portion 326 and theadjustment collar 310 engaged to thethread form 330, thewire clip 400 is fitted over thenose portion 326 generally perpendicular to the longitudinal axis of theclutch sleeve 300 such thatlegs 404 are engaged toleg apertures 408 in theclutch sleeve 300 and thebase 402 is disposed in a shallowU-shaped recess 410 that is situated on the top surface of thenose portion 326 as best shown inFigure 4. Engagement of thewire clip 400 into theleg apertures 408 andrecess 410 operatively locks thewire clip 400 to thenose portion 326 and thereby creates a positive stop that is configured to prevent theadjustment collar 310 from being threaded out of engagement with thethread form 330 that is formed onto thenose portion 326.
Theclutch cover 314 is constructed in the form of a hollow sleeve that shrouds theclutch plate 306, thespring 308, thenose portion 326 and thewire clip 400. Theclutch cover 314 extends forwardly of thebase portion 324 and includes agripping surface 420 that is formed on its outer perimeter. Thegripping surface 420 is contoured to permit the user of thepower tool 10 to rotate theclutch cover 314 about the longitudinal axis of thepower tool 10 to adjust the setting of theclutch mechanism 18 as will be discussed in greater detail, below.
A plurality ofmating engagement teeth 422 are formed onto the inner diameter of theclutch cover 314 which are sized to engage theengagement teeth 384a of theadjustment collar 310. Themating engagement teeth 422 are relatively longer than theengagement teeth 384a and as such, permit theengagement teeth 384a to axially slide along themating engagement teeth 422 along the longitudinal axis of thepower tool 10 when theclutch cover 314 is rotated.
In the example provided, thedetent mechanism 312 is illustrated to include adetent spring 430, aplunger 432 and adetent ring 434. Thedetent spring 430 andplunger 432 are housed in the detent aperture 338 that is formed through thebase portion 324 of theclutch sleeve 300. Thedetent spring 430, which is illustrated to be a conventional compression spring, abuts thegear case 100 on a first side and a flattened end of theplunger 432 on the opposite side, thereby biasing theplunger 432 in a direction outwardly from thebase portion 324. Theplunger 432 includes acontact end 440, which is defined by a spherical radius in the example illustrated, and which is biased forwardly by thedetent spring 430 into contact with thedetent ring 434. In the particular embodiment provided, thedetent ring 434 is integrally formed with theclutch cover 314 and includes a plurality of circumferentially spaced recesses ordetents 442 that are sized to engage thecontact end 440 of theplunger 432. Each of thedetents 442 is illustrated to be defined by a spherical radius that conforms to thecontact end 440. A setting indicator 450 (Figure 2) may be employed to indicate the position of theadjustment collar 310 relative to theclutch sleeve 300. In the example provided, the settingindicator 450 includes anarrow 452 that is formed into thehandle shells 34 and ascale 454 that is marked into the circumference of theclutch cover 314.
Rotation of theclutch cover 314 relative to theclutch sleeve 300 causes theadjustment collar 310 to rotate in an equivalent manner to thereby alter the amount by which thespring 308 is compressed. Interaction between thecontact end 440 of theplunger 432 and thedetents 442 in thedetent ring 434 provide the user of thepower tool 10 with feedback as to the setting of theclutch mechanism 18, as well as inhibit theclutch cover 314 from inadvertently rotating out of the position to which it has been set. Thespring 308 exerts a compression force onto theannular flange 380 of theadjustment collar 310 and theplate member 360 of theclutch plate 306, driving theleg members 362 of theclutch plate 306 rearwardly and biasing theballs 304 into engagement with theclutch face 222. Theballs 304 exert a counter torque onto theclutch face 222 that tends to inhibit rotation of thethird ring gear 202 relative to theclutch sleeve 300.
When thepower tool 10 is operated and the torque that is exerted through thegear teeth 202a of thethird ring gear 202 exceeds the counter torque, thepeaks 224 of theclutch face 222 ride over theballs 304 to enable thethird ring gear 202 to rotate relative to thethird reduction carrier 204 and greatly reduce the torque that is applied to theoutput spindle assembly 20.
While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the claims.

Claims

A hand-held power tool (10) comprising:
a housing (12);
a handle coupled to the housing;
a multi-speed transmission (16) having a gear case (100) and a gear train (102), the gear case associated with the housing and housing the gear train, the gear train being operable for performing a speed reduction and torque multiplication function;
a clutch (18) having a clutch member (302), an engagement member (304), a clutch plate (306), a clutch spring (308) and a clutch sleeve (300), the clutch member being associated with the multi-speed transmission and including a clutch face (222), the clutch spring and the clutch plate cooperating to bias the engagement member into engagement with the clutch face to resist rotation of the clutch member, the clutch sleeve supporting the clutch plate and the clutch spring; and
characterised by a pair of first tabs (104) coupled to one of the gear case and the clutch sleeve, each of the fastening tabs defining a coupling recess (114) that extend in a direction that is transverse to a longitudinal axis of the one of the gear case and the clutch sleeve;
a pair of second tabs (334) coupled to the other one of the gear case and the clutch sleeve, each second tab including a pin aperture (340) and being configured to slidingly receive a corresponding one of the first tabs such that the pin aperture is aligned to the coupling recess; and
a pair of pin members (350), each pin member being disposed into the coupling recess of an associated first tab and the pin aperture of an associated second tab to thereby inhibit withdrawal of the first and second tabs from one another.
The hand-held power tool of Claim 1, wherein the clutch further comprises an adjustment collar (310) threadably engaged to the clutch sleeve and wherein rotation of the adjustment collar affects an amount by which the clutch spring is compressed against the clutch plate.
The hand-held power tool of Claim 2, wherein a pair of collar securing apertures (408) are formed in the clutch sleeve, each of the collar securing apertures extending in a direction that is transverse to a longitudinal axis of the clutch sleeve and being configured to receive a collar securing pins (404), the collar securing pins cooperating with the clutch sleeve to limit movement of the adjustment collar along the clutch sleeve in a predetermined direction.
The hand-held power tool of Claim 3, wherein each of the collar securing pins is an opposite leg of a clip (402), the clip including a base portion having opposite ends, each opposite end being coupled to an associated one of the legs.
The hand-held power-tool of Claim 4, wherein the clutch sleeve includes a slot that is configured to receive the base portion of the clip when the legs of the clip are inserted to the collar securing apertures.
The hand-held power tool of Claim 3, wherein the collar securing pins are generally cylindrical in shape.
The hand-held power tool of Claim 1, wherein each of the second tabs is a container-like structure having an two spaced apart wall members (344, 346), which extend outwardly from the other one of the gear case and the clutch sleeve, and an outer wall member (342) that is spaced outwardly from the other one of the gear case and the clutch sleeve and interconnects the two spaced apart wall members.
The hand-held power tool of Claim 7, wherein the pin apertures extend completely through the two spaced apart wall members.
The hand-held power tool of Claim 1, wherein the coupling recess is generally U-shaped.
The hand-held power tool of Claim 1, wherein the pin members are generally cylindrically shaped.